1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/modules/zlib/src/adler32.c Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,179 @@
1.4 +/* adler32.c -- compute the Adler-32 checksum of a data stream
1.5 + * Copyright (C) 1995-2011 Mark Adler
1.6 + * For conditions of distribution and use, see copyright notice in zlib.h
1.7 + */
1.8 +
1.9 +/* @(#) $Id$ */
1.10 +
1.11 +#include "zutil.h"
1.12 +
1.13 +#define local static
1.14 +
1.15 +local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2));
1.16 +
1.17 +#define BASE 65521 /* largest prime smaller than 65536 */
1.18 +#define NMAX 5552
1.19 +/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
1.20 +
1.21 +#define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;}
1.22 +#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
1.23 +#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
1.24 +#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
1.25 +#define DO16(buf) DO8(buf,0); DO8(buf,8);
1.26 +
1.27 +/* use NO_DIVIDE if your processor does not do division in hardware --
1.28 + try it both ways to see which is faster */
1.29 +#ifdef NO_DIVIDE
1.30 +/* note that this assumes BASE is 65521, where 65536 % 65521 == 15
1.31 + (thank you to John Reiser for pointing this out) */
1.32 +# define CHOP(a) \
1.33 + do { \
1.34 + unsigned long tmp = a >> 16; \
1.35 + a &= 0xffffUL; \
1.36 + a += (tmp << 4) - tmp; \
1.37 + } while (0)
1.38 +# define MOD28(a) \
1.39 + do { \
1.40 + CHOP(a); \
1.41 + if (a >= BASE) a -= BASE; \
1.42 + } while (0)
1.43 +# define MOD(a) \
1.44 + do { \
1.45 + CHOP(a); \
1.46 + MOD28(a); \
1.47 + } while (0)
1.48 +# define MOD63(a) \
1.49 + do { /* this assumes a is not negative */ \
1.50 + z_off64_t tmp = a >> 32; \
1.51 + a &= 0xffffffffL; \
1.52 + a += (tmp << 8) - (tmp << 5) + tmp; \
1.53 + tmp = a >> 16; \
1.54 + a &= 0xffffL; \
1.55 + a += (tmp << 4) - tmp; \
1.56 + tmp = a >> 16; \
1.57 + a &= 0xffffL; \
1.58 + a += (tmp << 4) - tmp; \
1.59 + if (a >= BASE) a -= BASE; \
1.60 + } while (0)
1.61 +#else
1.62 +# define MOD(a) a %= BASE
1.63 +# define MOD28(a) a %= BASE
1.64 +# define MOD63(a) a %= BASE
1.65 +#endif
1.66 +
1.67 +/* ========================================================================= */
1.68 +uLong ZEXPORT adler32(adler, buf, len)
1.69 + uLong adler;
1.70 + const Bytef *buf;
1.71 + uInt len;
1.72 +{
1.73 + unsigned long sum2;
1.74 + unsigned n;
1.75 +
1.76 + /* split Adler-32 into component sums */
1.77 + sum2 = (adler >> 16) & 0xffff;
1.78 + adler &= 0xffff;
1.79 +
1.80 + /* in case user likes doing a byte at a time, keep it fast */
1.81 + if (len == 1) {
1.82 + adler += buf[0];
1.83 + if (adler >= BASE)
1.84 + adler -= BASE;
1.85 + sum2 += adler;
1.86 + if (sum2 >= BASE)
1.87 + sum2 -= BASE;
1.88 + return adler | (sum2 << 16);
1.89 + }
1.90 +
1.91 + /* initial Adler-32 value (deferred check for len == 1 speed) */
1.92 + if (buf == Z_NULL)
1.93 + return 1L;
1.94 +
1.95 + /* in case short lengths are provided, keep it somewhat fast */
1.96 + if (len < 16) {
1.97 + while (len--) {
1.98 + adler += *buf++;
1.99 + sum2 += adler;
1.100 + }
1.101 + if (adler >= BASE)
1.102 + adler -= BASE;
1.103 + MOD28(sum2); /* only added so many BASE's */
1.104 + return adler | (sum2 << 16);
1.105 + }
1.106 +
1.107 + /* do length NMAX blocks -- requires just one modulo operation */
1.108 + while (len >= NMAX) {
1.109 + len -= NMAX;
1.110 + n = NMAX / 16; /* NMAX is divisible by 16 */
1.111 + do {
1.112 + DO16(buf); /* 16 sums unrolled */
1.113 + buf += 16;
1.114 + } while (--n);
1.115 + MOD(adler);
1.116 + MOD(sum2);
1.117 + }
1.118 +
1.119 + /* do remaining bytes (less than NMAX, still just one modulo) */
1.120 + if (len) { /* avoid modulos if none remaining */
1.121 + while (len >= 16) {
1.122 + len -= 16;
1.123 + DO16(buf);
1.124 + buf += 16;
1.125 + }
1.126 + while (len--) {
1.127 + adler += *buf++;
1.128 + sum2 += adler;
1.129 + }
1.130 + MOD(adler);
1.131 + MOD(sum2);
1.132 + }
1.133 +
1.134 + /* return recombined sums */
1.135 + return adler | (sum2 << 16);
1.136 +}
1.137 +
1.138 +/* ========================================================================= */
1.139 +local uLong adler32_combine_(adler1, adler2, len2)
1.140 + uLong adler1;
1.141 + uLong adler2;
1.142 + z_off64_t len2;
1.143 +{
1.144 + unsigned long sum1;
1.145 + unsigned long sum2;
1.146 + unsigned rem;
1.147 +
1.148 + /* for negative len, return invalid adler32 as a clue for debugging */
1.149 + if (len2 < 0)
1.150 + return 0xffffffffUL;
1.151 +
1.152 + /* the derivation of this formula is left as an exercise for the reader */
1.153 + MOD63(len2); /* assumes len2 >= 0 */
1.154 + rem = (unsigned)len2;
1.155 + sum1 = adler1 & 0xffff;
1.156 + sum2 = rem * sum1;
1.157 + MOD(sum2);
1.158 + sum1 += (adler2 & 0xffff) + BASE - 1;
1.159 + sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
1.160 + if (sum1 >= BASE) sum1 -= BASE;
1.161 + if (sum1 >= BASE) sum1 -= BASE;
1.162 + if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1);
1.163 + if (sum2 >= BASE) sum2 -= BASE;
1.164 + return sum1 | (sum2 << 16);
1.165 +}
1.166 +
1.167 +/* ========================================================================= */
1.168 +uLong ZEXPORT adler32_combine(adler1, adler2, len2)
1.169 + uLong adler1;
1.170 + uLong adler2;
1.171 + z_off_t len2;
1.172 +{
1.173 + return adler32_combine_(adler1, adler2, len2);
1.174 +}
1.175 +
1.176 +uLong ZEXPORT adler32_combine64(adler1, adler2, len2)
1.177 + uLong adler1;
1.178 + uLong adler2;
1.179 + z_off64_t len2;
1.180 +{
1.181 + return adler32_combine_(adler1, adler2, len2);
1.182 +}
